Dual fuel generator

ABSTRACT

A control circuit for a dual fuel generator includes a primary fuel valve to control the supply of a primary fuel, a secondary fuel valve to control the supply of a secondary fuel, a primary fuel pressure switch to detect the primary fuel, a secondary fuel pressure switch to detect the secondary fuel, and a controller. The controller is configured to receive a primary signal for availability of the primary fuel from the primary fuel pressure switch and a secondary signal for availability of the secondary fuel from the secondary and operate the primary fuel valve and the secondary fuel valve in response to the primary signal and the secondary signal. When the secondary fuel valve is open so that the secondary fuel is provided to the dual fuel generator, the control circuit is configured to ground the primary signal by connecting the primary fuel pressure switch to ground.

CROSS REFERENCE TO PRIOR APPLICATION

This application claims priority benefit of Provisional Application No.62/829,779 (Docket No. 010222-19003A) filed Apr. 5, 2019, which ishereby incorporated by reference in its entirety.

FIELD

This disclosure is in the field of an engine-generator set, which may bereferred to as a generator or a genset, that includes an engine and analternator or another device for generating electrical energy or power.

BACKGROUND

One or more generators may provide power to a load through a generatorbus. The generator bus is an electrical conductive path and may beselectively connected through multiple circuit breakers or other typesof switches to the generators, the utility system, and other devices. Toavoid interruption of power to the load, some generators may includemultiple sources of fuel. When one source of fuel becomes unavailable,the generator may switch to another source of fuel. A variety ofscenarios may result in switching between the multiple sources of fuelat inappropriate times.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate a valve system for the dual fuel generator.

FIGS. 2A and 2B illustrate a control system for the dual fuel generator.

FIG. 2C illustrates an embodiment of the control system for the dualfuel generator.

FIG. 2D illustrates an example sequence for the scenarios of FIGS. 3-7.

FIG. 3 illustrates a first scenario for a control circuit for thecontrol system of the dual fuel generator.

FIG. 4 illustrates a second scenario for a control circuit for thecontrol system of the dual fuel generator.

FIG. 5 illustrates a third scenario for a control circuit for thecontrol system of the dual fuel generator.

FIG. 6 illustrates a fourth scenario for a control circuit for thecontrol system of the dual fuel generator.

FIG. 7 illustrates a fifth scenario for a control circuit for thecontrol system of the dual fuel generator.

FIG. 8 illustrates an example generator controller, or enginecontroller, of the system of FIGS. 1-7.

FIG. 9 illustrates an example flowchart for the control system of FIGS.3-7 or the controller(s) of FIG. 8.

DETAILED DESCRIPTION

A generator or generator set may include multiple fuel sources such as aprimary fuel source and a secondary fuel source. The primary fuel sourcemay be a utility fuel source (e.g., natural gas) that is provided to thegenerator through a pipeline system. The secondary fuel source may bestored in a tank under pressure (e.g., liquified petroleum gas). Thegenerator may include a fuel supply inlet including at least one pipeand at least one valve for each of the multiple fuel sources (i.e.,primary fuel inlet and valve for the primary fuel and secondary fuelinlet and valve for the secondary fuel). Another number of fuels may beused such as three fuels, for fuels, or more.

The generator may operate using the primary fuel source until aninterruption event occurs. The interruption event may include a localmalfunction in which one or more components associated with thegenerator and primary fuel source are not fully operational. Theinterruption event may include maintenance or an instruction from atechnician or administrator device sent remotely to the generator. Theinterruption event may include intervention by a user or technicianprovided locally to the generator. The interruption event may be anatural event such as a seismic event that causes primary fuel sourcedamage (pipeline, etc).

In response to the interruption event, the generator may deactivate theprimary fuel source and activate the secondary fuel source. In responseto the interruption event, the generator may switch from the primaryfuel source to the secondary fuel source through operating one or morevalves, for example, by closing the primary fuel inlet and valve andopening the secondary fuel inlet and valve. For example, in the event ofa loss of a primary fuel supply, a second fuel source may be fitted tothe engine, and selected either manually or with an automatic changeoversystem. The automatic changeover system typically uses a combination ofelectrically operated valves to control which fuel source is supplyingthe engine. Both fuel source valves are controlled by an enginecontroller or engine controller module (ECM). The engine control moduledetects availability of the primary fuel source using a pressure switchlocated on the supply side of the fuel valve. When pressure drops belowa threshold, the pressure switch actuates, grounding the signal wire toindicate a loss of fuel. The ECM enables an output to energize thesecondary fuel source solenoid, and then de-energizes the primary fuelsolenoid to close the valve.

At some point, the generator switches back to the primary fuel source.This may be done automatically after a certain time period. However,some challenges may result from or are otherwise apparent due toautomatically switching back to the primary fuel source and may includeleaking, backfiring, or other malfunctions of the generator.Specifically, commercially available gas valves allow for a small amountof reverse leakage. In a dual fuel system that is operating on asecondary fuel source, the secondary fuel may leak through the primaryfuel valve into the depleted primary fuel source's fuel lines. In suchan instance, a pressure switch monitoring the primary fuel source mayprovide a false positive signal to the ECM. When this occurs, the enginecontroller detects that the primary fuel source has returned, andsubsequently switches the engine's fuel source from secondary to primaryfuel. This may result in causing the engine to stutter and potentially,cause shutdown or disablement of the system. Similar outcomes may occurwhen the primary fuel source is available, but with low or inconsistentpressure.

The following embodiments include a control system for a dual fuelgenerator that prevents undesired automatic switching of the fuel sourceof the generator. A feedback control circuit is employed to override theprimary fuel source feedback signal when the engine has selected asecondary fuel source, thereby preventing nuisance fuel changeoverevents and increasing overall system reliability. As described in moredetail below, an additional pressure switch may be installed on thesupply side of the secondary fuel source.

FIGS. 1A and 1B illustrate a valve system for the dual fuel generator.The valve system for the dual fuel generator includes at least twovalves, a primary fuel valve 10 and a secondary fuel valve 11. Asillustrated, the valve system for the dual fuel generator includes threevalves, which also includes a supply valve 12 downstream of both theprimary fuel inlet and the secondary fuel inlet.

FIGS. 2A and 2B illustrate a control system for the dual fuel generator.The control system includes an engine controller (e.g., engine controlmodule), one or more switches, and one or more indicators. Asillustrated, the control system includes an operator control interface15 including a dual fuel reversion switch 17 and an illuminator 16. Theilluminator 16 may be a light, light emitting diode, or lamp thatindicates when the secondary fuel source is activated. The lightindicates that the secondary fuel source is in use and that the controlsystem is currently configured to receive the command from the user toinitiate the generator switching from the secondary fuel source to theprimary fuel source. Alternatively, the function of the illuminator 16may be performed by a display screen (e.g., user interface).

Additional inputs to the control system may be provided through maininterface 20. The operator control interface is configured to receive acommand from a user (e.g., technician) to initiate the generatorswitching from the secondary fuel source to the primary fuel source. Thecontrol system prevents the automatic transition from the secondary fuelsource to the primary fuel source until the operator control interfacereceive the command from the user.

FIG. 2C illustrates an example control system and/or control circuitincluding engine controller 100, driving circuit 30 and sensing circuit40. The engine controller 100 may be an engine control module (ECM) orengine control unit (ECU) configured for one or more other enginefunctions. For example, the engine controller 100 may generate timingsignals for one or more cylinders for a combustion cycle, control air tofuel ratio based on sensor measurements, control idle speed, controlvalve timing, and/or other functions. Other systems in the engine mayinclude a fuel tank, a fuel line, a retractable starter, a starterhandle, an air cleaning system, a muffler, a control portion, a governorsystem, a throttle system, and a lubrication system.

Alternatively, rather than the engine controller 100 the control circuitmay include a generator controller configured for one or more otherfunctions of a generator. The generator controller may perform fieldsignal control, load balancing, generator paralleling, generatorsynchronization, or other generator functions. Other components of thegenerator may include a rotor, a stator, and field windings.

FIG. 2D illustrated the sequence of events depicted in FIGS. 3-7 for thecontrol circuit or the control system of the dual fuel generator. InFIG. 3, the initial state, the both fuels are available and thegenerator is running on the primary fuel. In FIG. 4, the primary fuelbecomes unavailable, and the generator switches to the secondary fuel.In FIG. 5, the primary fuel becomes available, but the generator remainsusing the secondary fuel. Three subsequent options are possible. First,as shown in FIG. 6, the secondary fuel becomes available, and thegenerator switches back to the primary fuel. Second, as shown in FIG. 7,a user or a signal indicates a reset, which causes the generator toswitch back to the primary fuel. Third, another external event, such asa remote command, user intervention, or unavailable of all fuel sources,causes the generator to shut down.

The control circuit may include a driving circuit 30 that is at leastpartially electrically isolated from a sensing circuit 40. The drivingcircuit 30 provides at least a primary fuel valve signal and a secondaryfuel valve signal to the engine controller. The control circuit includesa power source 31 coupled to one or more relay coils 39 and theindicator or illuminator 37 (e.g., lamp). In the sensing circuit, on thecontrol side of the relay, are relay contacts 41, which may be normallyopen relay contacts. The sensing circuit 40 may also include a userswitch (e.g., momentary reset switch 47), a primary fuel pressure switch43 (e.g., pressure sensor) and a secondary fuel pressure switch 45(e.g., pressure sensor). The primary fuel pressure switch 43 detects theexisting of fuel pressure in the primary inlet or other pipe associatedwith the primary fuel source. The secondary fuel pressure switch 45detects the existing of fuel pressure in the secondary inlet or otherpipe associated with the secondary fuel source. The primary fuelpressure switch 43 is a sensor that detects whether the primary fuelsource is available. The secondary fuel pressure switch 45 is a sensorthat detects whether the secondary fuel source is available. It shouldbe noted that normally closed relay contacts may be used withcorresponding changes in the circuit to maintain the logical sequencesdescribed herein.

FIG. 3 illustrates an initial scenario in which both the primary fuelsupply and the secondary fuel supply are available to the generator. Inthe initial scenario, the control circuit provides the primary fuelvalve signal for a primary fuel valve to the controller 100. Thecontroller 100 may include a corresponding primary fuel valve switch tocontrol the supply of a primary fuel to the dual fuel generator via theprimary fuel valve. The primary fuel valve signal maintains the primaryfuel valve open in order to provide the primary fuel to the generator.

FIG. 4 illustrates a primary fuel unavailable scenario that occurs afterthe initial scenario. In the primary fuel unavailable scenario, theprimary fuel is unavailable due to an interruption of event such as lossof utility, leak, or user intervention. The availability of primary fuelmay be detected by the primary fuel pressure switch. In response, thecontrol circuit provides the secondary fuel valve signal, correspondingto the secondary fuel valve, to the engine controller 100. Thecontroller 100 may include a secondary fuel valve switch to control thesupply of a secondary fuel to the dual fuel generator via a secondaryfuel valve. The secondary fuel valve signal maintains the secondary fuelvalve open in order to provide secondary fuel to the generator. Inaddition, in the primary fuel unavailable scenario, the relay contactsare closed, which turns on the illuminator 37, which is powered throughthe power source 31.

FIG. 5 illustrates a scenario in which after the interruption event hasoccurred, the primary fuel source becomes available again. In this case,the generator continues to use the secondary fuel source even though theprimary fuel source is available. The primary fuel pressure switch,which is normally closed, is opened, but the generator continues to usethe secondary fuel source. The control circuit prevents the generatorfrom automatically switching back to the primary fuel even though theprimary fuel has become available. It should be noted that a primaryfuel switch that is normally open may be used with corresponding changesin the circuit to maintain the logical sequences described herein.

The secondary fuel pressure switch 45 connected to the supply side ofthe secondary fuel source is open under no pressure, and the pressureswitch contacts are normally closed when secondary fuel is available.Further, the common and normally closed contacts of the secondary fuelpressure switch 45 are connected to the normally closed contact of themomentary switch 47 and the feedback signal from the primary fuelpressure switch 43. It should be noted that a secondary fuel pressureswitch that is normally open may be used with corresponding changes inthe circuit to maintain the logical sequences described herein.Likewise, a momentary switch that is normally open may be used withcorresponding changes in the circuit to maintain the logical sequencesdescribed herein.

The common contact of the momentary switch 47 connects to a normallyopen relay contact 41, and the common relay contact 41 is connected tosystem ground. The relay's coil 39 as well as illuminator 37 areconnected in parallel with the secondary fuel solenoid coil. When thesecondary fuel source is enabled, the illuminator 37 lights to indicatethe system is operating on the secondary fuel source, and the relaycontacts close, grounding the primary fuel source feedback signal.Grounding the feedback signal effectively short circuits the primaryfuel pressure switch 43 to ground, such that the feedback signal to thecontroller 100 indicates that primary fuel is lost, regardless of thestate of the primary fuel pressure switch 43. In this condition, theengine controller 100 is unable to detect the return of primary fuelpressure due to actual availability or a nuisance event. The engine willcontinue to operate on the secondary fuel source until another eventoccurs to change the state shown in FIG. 5.

FIG. 6 illustrates a scenario in which after the interruption event andafter running on secondary fuel, the secondary fuel becomes unavailable.The secondary fuel may become unavailable because the tank is empty orfrom a malfunction. The unavailability of the secondary fuel may bedetected by the secondary fuel pressure switch. The secondary pressureswitch contacts are open, which disconnects the primary pressure switchoverride caused by grounding the primary fuel pressure switch 43. Inresponse to the secondary fuel being unavailable, the primary fuel valvesignal is turned on. In response to the secondary fuel beingunavailable, the relay resets (switched to open), which turns off theilluminator to indicate that the secondary fuel source is not in use.The engine controller 100 attempts to switch to primary fuel if it isavailable. If primary fuel is not available, the engine may shutdown dueto loss of fuel.

FIG. 7 illustrates an internal intervention scenario in which after theinterruption event, after running on secondary fuel, and after primaryfuel becomes available, the switch 47 (e.g., momentary switch) isactivated. The switch 47 may be physically flipped by a technician orother user in the presence of the generator. Activating the switch 47disconnects the primary pressure switch override caused by grounding theprimary fuel pressure switch 43. The switch 47 may be operated while thegenerator is running. In response to activation of the switch 47, thesecondary fuel valve signal is turned off and the secondary fuel valveis closed. In response to the activation of the switch 47, the primaryfuel valve signal is turned back on and the primary fuel is provided tothe generator. In response to activation of the switch 47, the relayresets (switched to open) and the illuminator is turned off.

In the case that the controller 100 is a generator set controller, thegenerator set controller monitors the status of primary and secondaryfuel pressures as well as status of the fuel valve solenoids. Upon lossof available primary fuel pressure, the generator set controller enablesa relay, relay drive output, or other grounding output type to overridethe primary fuel source feedback signal. The controller may also providediagnostic information about the fuel sources and outage events to auser locally or remotely, and may also provide indication of the activefuel source, and a means for a user to attempt a changeover back toprimary fuel.

The generator controller may also determine a generator rating. Becausethe generator is operable on different types of fuel, the generator mayalso operate with different operating characteristics over time. One ofthe operating characteristics that may change when fuel type changes isthe maximum output of the generator, which may be referred to as thegenerator rating. The generator rating may be variable and changebetween a first value when the primary fuel is used, or when the primaryfuel valve is open, and a second value when the secondary fuel is used,or when the secondary fuel valve is open. In some dual fuel generators,the generator rating for LP (typically the secondary fuel) is higherthan NG (typically the primary fuel).

The generator controller may calculate or determine the variablegenerator rating based on whether operation of the primary fuel valve orthe secondary fuel valve. In one example, the generator controllerdetermines the rating from a lookup table. In another example, themakeup of the fuel is detected by a sensor and the rating is calculatedfrom the makeup of the fuel. The generator controller may act on theload information or send it out to switchgear or other device to makethe load shed determination. Additionally, the controller may adjust itsload rating based on fuel pressure or makeup.

The generator controller may initiate the changeover between the primaryfuel and the secondary fuel based on load. That is, rather than apressure switch or sensor detecting an absence in the primary fuel, theswitch to the secondary fuel may be based on the load. For example, thesecondary fuel may be capable of providing a higher power output,corresponding to a higher load on the generator. As described in otherembodiments herein, once the generator has been changed to the secondaryfuel, the control circuit may be prevent the generator from returning tothe primary fuel unless certain external conditions are present. Thosecertain external conditions may be user input, loss of secondary fuel,and in this example, also a change in the load on the generator.

The generator controller may also control loads on the dual fuelgenerator based on the type of fuel that is being used. Because theoutput of the generator depends on fuel type, the amount of load thatthe generator can handle or efficiently handle also depends on the fueltype. The generator controller may receive data indicative of the loadson the generator in power. The generator may compare the loads on thegenerator to the determined generator rating. When the connected loadsexceed a threshold, the generator controller may generate a load commandthat instructs one or more load to be removed from or added to thegenerator. The load command may be associated to a first load level whenthe primary fuel valve is open and a second load level when thesecondary fuel valve is open.

In the case the controller 100 is an ECM, the ECM monitors the status ofprimary and secondary fuel pressures. Upon loss of available primaryfuel pressure, the ECM performs a changeover to the secondary fuelsource, and henceforth ignores the status of the primary fuel pressureswitch until a button press or car area network (CAN) command isreceived to command an attempted changeover to the primary fuel source,or the secondary fuel pressure switch indicates secondary fuel is lost.The ECM may also provide diagnostic information about the fuel sourcesand outage events via local I/O pins or over the CAN bus.

In addition or in the alternative of the scenarios described withrespect to FIGS. 6 and 7, an external intervention event may also occur.Rather than the manual switch to change the fuel supply back to theprimary in the internal intervention, the external intervention is anautomated or manual command to shut down the generator. The externalintervention may be received from a user that turns off the generator.The external intervention may be received from a generator controllerthat provides a shutdown signal based on another factor. The generatorcontroller may shut down the generator when it is no longer needed. Forexample, a utility may have come back online, the load may have changed,or another generator may have come online, rendering the generatorunnecessary at the present time for the system. The externalintervention may come from an error or malfunction such as loss of allfuel sources, loss of field, mechanical problems, electrical problems,or other problems.

FIG. 8 illustrates an example generator controller 100, or enginecontroller, of the system of FIGS. 1-7. The controller 100 may include aprocessor 300, a memory 302, and a communication interface 303. Thegenerator controller 100 may be connected to a workstation 309 oranother external device (e.g., control panel) and/or a database 307.Optionally, the generator controller 100 may include an input device 305and/or a sensing circuit 311. The sensing circuit 311 receives sensormeasurements for the operation of the primary and secondary fuel source.The input device 305 may include the momentary reset switch. The memory302 may store instructions for analyzing the sensor data from thesensing circuit 311 and/or the inputs from the input device 305.

FIG. 9 illustrates an example flowchart for operation of the controller100 and/or the system of FIGS. 1-7. The methods in FIG. 9 may, in someinstances, be implemented as logic or software executable by thecontroller 100. Additional, different, or fewer acts may be provided.The acts may be performed in the order shown or other orders. The actsmay also be repeated.

At act S101, the generator controller 100 receives sensor data from thesensing circuit 311 for the availability of the primary fuel source, orboth the primary and second fuel source. The availability may be abinary value (e.g., whether or not the corresponding pressure switch isactuated). The generator controller 100 may receive a primary signal foravailability of the primary fuel from the primary fuel pressure switchand a secondary signal for availability of the secondary fuel from thesecondary and operate the primary fuel valve switch and the secondaryfuel valve switch in response to the primary signal and the secondarysignal.

At act S103, the generator controller 100 switches the generator fromthe primary fuel source to the secondary fuel source. The generatorcontroller 100 may close one or more valves associated with the primaryfuel source and open one or more valves associated with the secondaryfuel source. The generator controller 100 may also switch one or moreparameters from the first fuel source to the second source. For example,parameters for operating the engine may depend on the fuel source (i.e.,the engine runs on different settings for natural gas than for liquifiedpetroleum).

At act S105, the generator controller 100 grounds a circuit elementassociated with the primary fuel source in response from to thechangeover from the primary fuel source to the secondary fuel source.The generator controller 100 may cause a relay to close that provides apath between the circuit element and ground. The circuit element may bea switch, a transistor, or a microcontroller. As an alternative to thecircuit element, the generator controller 100 may ground a wire or otherelectrical connection to ground the detection of the primary fuel.

At act S107, the generator controller 100 continues the monitor theavailability of the fuel sources through the sensing circuit 311. Theavailability of a fuel source may be determined based on pressure switchsignals received at the generator controller 100 from the fuel pressureswitches (e.g., primary fuel pressure switch 43 and secondary fuelpressure switch 45). The generator controller 100 may implementgrounding of the primary signal when (e.g., at the same time) thesecondary fuel is provided to the dual fuel generator. The generatorcontroller 100 may connect the primary fuel pressure switch to a groundin the control circuit by opening or closing one or more electricalpaths. For example, referring to the scenarios of FIGS. 3-7, the openingof the primary fuel pressure switch 43 that is normally closed providesthe path to ground. In addition, closing the normally open relaycontacts 41 can provide a path to ground. The relay is energized byactivation of the secondary fuel valve and the relay grounds the primarysignal by connecting the primary fuel pressure switch to ground.

That is, when the secondary fuel pressure switch 45 is normally closed(indicating pressure at the secondary fuel source) and the reset switch47 is closed, a path to ground is provided to the engine controller 100and the primary fuel pressure switch 43. In one sense, pressing thereset switch 47, generates a reset signal that disconnect the primaryfuel pressure switch from ground. The reset signal activates the primaryfuel valve switch and deactivate the secondary fuel valve switch inresponse to the user input and the detected availability of the primaryfuel.

The connection of the primary fuel pressure switch 43 to ground preventsthe operation of the primary fuel valve. The connection to ground causesthe generator controller 100 not to detect the operation of the primaryfuel pressure switch 43 even if it is closed.

The generator controller 100 may implement a switch activation time ordebounce time that prevents nuisance switching. The switch activationtime may be a user entered or automatically determined delay time. Thegenerator controller 100 does not take any action upon a change in thestate of the pressure switch until the change has occurred for aduration equal or greater than the delay time. The delay time isselected so that the amount of time that the pressure dips below theswitch threshold is long enough to prevent nuisance switching back andforth if the pressure is hovering around the threshold for the pressureswitch. Examples for the delay time may be 125 milliseconds, 250milliseconds, 500 milliseconds, or 1 second.

The generator controller 100 may be configured for a testing routinewhere the user provides varying amount of fuel pressure to the pressureswitches and the debouncing responses of the switches is detected by thegenerator controller 100. The generator controller 100 may analyze thedebouncing response and select and apply a delay time that prevents asubstantial portion of the debouncing responses.

At act S109, the generator controller 100 receives user input from theinput device 305. The user input may be a request to return thegenerator to normal operation or otherwise switch to the primary fuelsource. The user may depress a button or other switching device togenerate the user input. Alternatively, through the communicationinterface 303 or workstation 309, the user may transmit the user inputelectronically or wireless. In one example, the user may provide theuser input through a smart phone or other portable mobile device.

At act S111, the generator controller 100 switches the generator fromthe secondary fuel source to the primary fuel source. The generatorcontroller 100 may open one or more valves associated with the primaryfuel source and close one or more valves associated with the secondaryfuel source. The generator controller 100 may first determine thatprimary fuel source is available and that the user input has beenreceived, and then in response to both the availability and the userinput, switch the fuel source of the generator back to the primary fuelsource. In addition, the generator controller 100 may change one or moreoperating parameters for the engine in response to the fuel change.

The processor 300 may include a general processor, digital signalprocessor, an application specific integrated circuit (ASIC), fieldprogrammable gate array (FPGA), analog circuit, digital circuit,combinations thereof, or other now known or later developed processor.The processor 300 may be a single device or combinations of devices,such as associated with a network, distributed processing, or cloudcomputing.

The memory 302 may be a volatile memory or a non-volatile memory. Thememory 302 may include one or more of a read only memory (ROM), randomaccess memory (RAM), a flash memory, an electronic erasable program readonly memory (EEPROM), or other type of memory. The memory 302 may beremovable from the network device, such as a secure digital (SD) memorycard.

In addition to ingress ports and egress ports, the communicationinterface 303 may include any operable connection. An operableconnection may be one in which signals, physical communications, and/orlogical communications may be sent and/or received. An operableconnection may include a physical interface, an electrical interface,and/or a data interface.

The communication interface 303 may be connected to a network. Thenetwork may include wired networks (e.g., Ethernet), wireless networks,or combinations thereof. The wireless network may be a cellulartelephone network, an 802.11, 802.16, 802.20, or WiMax network. Further,the network may be a public network, such as the Internet, a privatenetwork, such as an intranet, or combinations thereof, and may utilize avariety of networking protocols now available or later developedincluding, but not limited to TCP/IP based networking protocols.

While the computer-readable medium (e.g., memory 302 or database 307) isshown to be a single medium, the term “computer-readable medium”includes a single medium or multiple media, such as a centralized ordistributed database, and/or associated caches and servers that storeone or more sets of instructions. The term “computer-readable medium”shall also include any medium that is capable of storing, encoding orcarrying a set of instructions for execution by a processor or thatcause a computer system to perform any one or more of the methods oroperations disclosed herein.

In a particular non-limiting, exemplary embodiment, thecomputer-readable medium can include a solid-state memory such as amemory card or other package that houses one or more non-volatileread-only memories. Further, the computer-readable medium can be arandom access memory or other volatile re-writable memory. Additionally,the computer-readable medium can include a magneto-optical or opticalmedium, such as a disk or tapes or other storage device to capturecarrier wave signals such as a signal communicated over a transmissionmedium. A digital file attachment to an e-mail or other self-containedinformation archive or set of archives may be considered a distributionmedium that is a tangible storage medium. Accordingly, the disclosure isconsidered to include any one or more of a computer-readable medium or adistribution medium and other equivalents and successor media, in whichdata or instructions may be stored. The computer-readable medium may benon-transitory, which includes all tangible computer-readable media.

In an alternative embodiment, dedicated hardware implementations, suchas application specific integrated circuits, programmable logic arraysand other hardware devices, can be constructed to implement one or moreof the methods described herein. Applications that may include theapparatus and systems of various embodiments can broadly include avariety of electronic and computer systems. One or more embodimentsdescribed herein may implement functions using two or more specificinterconnected hardware modules or devices with related control and datasignals that can be communicated between and through the modules, or asportions of an application-specific integrated circuit. Accordingly, thepresent system encompasses software, firmware, and hardwareimplementations.

In accordance with various embodiments of the present disclosure, themethods described herein may be implemented by software programsexecutable by a computer system. Further, in an exemplary, non-limitedembodiment, implementations can include distributed processing,component/object distributed processing, and parallel processing.Alternatively, virtual computer system processing can be constructed toimplement one or more of the methods or functionality as describedherein.

As used in this application, the term ‘circuitry’ or ‘circuit’ refers toall of the following: (a) hardware-only circuit implementations (such asimplementations in only analog and/or digital circuitry) and (b) tocombinations of circuits and software (and/or firmware), such as (asapplicable): (i) to a combination of processor(s) or (ii) to portions ofprocessor(s)/software (including digital signal processor(s)), software,and memory(ies) that work together to cause an apparatus, such as amobile phone or server, to perform various functions) and (c) tocircuits, such as a microprocessor(s) or a portion of amicroprocessor(s), that require software or firmware for operation, evenif the software or firmware is not physically present.

This definition of ‘circuitry’ applies to all uses of this term in thisapplication, including in any claims. As a further example, as used inthis application, the term “circuitry” would also cover animplementation of merely a processor (or multiple processors) or portionof a processor and its (or their) accompanying software and/or firmware.The term “circuitry” would also cover, for example and if applicable tothe particular claim element, a baseband integrated circuit orapplications processor integrated circuit for a mobile phone or asimilar integrated circuit in server, a cellular network device, orother network device.

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andanyone or more processors of any kind of digital computer. Generally, aprocessor may receive instructions and data from a read only memory or arandom access memory or both. The essential elements of a computer are aprocessor for performing instructions and one or more memory devices forstoring instructions and data. Generally, a computer may also include,or be operatively coupled to receive data from or transfer data to, orboth, one or more mass storage devices for storing data, e.g., magnetic,magneto optical disks, or optical disks. Computer readable mediasuitable for storing computer program instructions and data include allforms of non-volatile memory, media and memory devices, including by wayof example semiconductor memory devices, e.g., EPROM, EEPROM, and flashmemory devices; magnetic disks, e.g., internal hard disks or removabledisks; magneto optical disks; and CD ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,special purpose logic circuitry.

The illustrations of the embodiments described herein are intended toprovide a general understanding of the structure of the variousembodiments. The illustrations are not intended to serve as a completedescription of all of the elements and features of apparatus and systemsthat utilize the structures or methods described herein. Many otherembodiments may be apparent to those of skill in the art upon reviewingthe disclosure. Other embodiments may be utilized and derived from thedisclosure, such that structural and logical substitutions and changesmay be made without departing from the scope of the disclosure.Additionally, the illustrations are merely representational and may notbe drawn to scale. Certain proportions within the illustrations may beexaggerated, while other proportions may be minimized. Accordingly, thedisclosure and the figures are to be regarded as illustrative ratherthan restrictive.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of the invention or of what may beclaimed, but rather as descriptions of features specific to particularembodiments of the invention. Certain features that are described inthis specification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable sub-combination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a sub-combination or variation of a sub-combination.

One or more embodiments of the disclosure may be referred to herein,individually and/or collectively, by the term “invention” merely forconvenience and without intending to voluntarily limit the scope of thisapplication to any particular invention or inventive concept. Moreover,although specific embodiments have been illustrated and describedherein, it should be appreciated that any subsequent arrangementdesigned to achieve the same or similar purpose may be substituted forthe specific embodiments shown. This disclosure is intended to cover anyand all subsequent adaptations or variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the description.

It is intended that the foregoing detailed description be regarded asillustrative rather than limiting and that it is understood that thefollowing claims including all equivalents are intended to define thescope of the invention. The claims should not be read as limited to thedescribed order or elements unless stated to that effect. Therefore, allembodiments that come within the scope and spirit of the followingclaims and equivalents thereto are claimed as the invention.

We claim:
 1. A control circuit for a dual fuel generator, the controlcircuit comprising: a primary fuel valve switch to control supply of aprimary fuel to the dual fuel generator via a primary fuel valve; asecondary fuel valve switch to control supply of a secondary fuel to thedual fuel generator via a secondary fuel valve; a primary fuel pressureswitch configured to detect availability of the primary fuel; asecondary fuel pressure switch configured to detect availability of thesecondary fuel; and a controller configured to receive a primary signalfor availability of the primary fuel from the primary fuel pressureswitch and a secondary signal for availability of the secondary fuelfrom the secondary and operate the primary fuel valve switch and thesecondary fuel valve switch in response to the primary signal and thesecondary signal, wherein when the secondary fuel is provided to thedual fuel generator, the control circuit is configured to ground theprimary signal by connecting the primary fuel pressure switch to ground.2. The control circuit of claim 1, wherein the connection of the primaryfuel pressure switch to ground prevents operation of the primary fuelvalve switch.
 3. The control circuit of claim 1, wherein the controlcircuit is configured to generate a reset signal that disconnect theprimary fuel pressure switch from ground.
 4. The control circuit ofclaim 3, wherein the reset signal activates the primary fuel valveswitch and deactivate the secondary fuel valve switch in response to auser input and the detected availability of the primary fuel.
 5. Thecontrol circuit of claim 1, wherein the controller is configured todetermine a variable generator rating based on operation of the primaryfuel valve or the secondary fuel valve.
 6. The control circuit of claim5, wherein the variable generator rating includes a first rating whenthe primary fuel valve is open and a second rating when the secondaryfuel valve is open.
 7. The control circuit of claim 1, wherein thecontroller is configured to generate a load command based on operationof the primary fuel valve or the secondary fuel valve.
 8. The controlcircuit of claim 7, wherein the load command is associated to a firstload level when the primary fuel valve is open and a second load levelwhen the secondary fuel valve is open.
 9. The control circuit of claim1, further comprising: a relay energized by activation of the secondaryfuel valve, wherein the relay grounds the primary signal by connectingthe primary fuel pressure switch to ground.
 10. The control circuit ofclaim 1, further comprising: an indicator configured to indicate thatthe secondary fuel valve switch is activated.
 11. The control circuit ofclaim 1, further comprising: a momentary switch configured to, whenactivated, disconnect the ground from the primary signal.
 12. A methodcomprising: receiving sensor data for availability of at least a primaryfuel source of a dual fuel generator; performing a changeover from theprimary fuel source to a secondary fuel source of the dual fuelgenerator; and grounding a circuit element associated with the primaryfuel source in response from to the changeover from the primary fuelsource to the secondary fuel source.
 13. The method of claim 12, whereina changeover from the secondary fuel source to the primary fuel sourceis prevented from the grounding of the circuit element associated withthe primary fuel source.
 14. The method of claim 12, further comprising:receiving updated sensor data for the availability of at least theprimary fuel source, the updated sensor data indicating that the primaryfuel source is operational, wherein a changeover from the secondary fuelsource to the primary fuel source is prevented from the grounding of thecircuit element associated with the primary fuel source.
 15. The methodof claim 12, further comprising: receiving a reset signal to stop thegrounding of the circuit element associated with the primary fuelsource.
 16. The method of claim 15, wherein the reset signal isgenerated by a switch actuation.
 17. The method of claim 12, furthercomprising: determining a variable generator rating based on operationof the primary fuel source or the secondary fuel source, wherein thevariable generator rating describes an output of the dual fuelgenerator.
 18. The method of claim 12, further comprising: generating aload command based on operation of the primary fuel source or thesecondary fuel source, wherein the load command connects or disconnectsa load for the dual fuel generator.
 19. A dual fuel generatorcomprising: a primary fuel valve to control supply of a primary fuel tothe dual fuel generator via a primary fuel valve; a secondary fuel valveto control supply of a secondary fuel to the dual fuel generator via asecondary fuel valve; a primary fuel pressure switch configured todetect availability of the primary fuel; a secondary fuel pressureswitch configured to detect availability of the secondary fuel; and acontrol circuit configured to receive a primary signal for availabilityof the primary fuel from the primary fuel pressure switch and asecondary signal for availability of the secondary fuel from thesecondary and operate the primary fuel valve switch and the secondaryfuel pressure switch in response to the primary signal and the secondarysignal, wherein when the secondary fuel is provided to the dual fuelgenerator, the control circuit is configured to ground the primarysignal by connecting the primary fuel pressure switch to ground.
 20. Thedual fuel generator of claim 19, wherein the connection of the primaryfuel pressure switch to ground prevents operation of the primary fuelvalve switch.